Fun and Games with the Dreaded Truss Rod

Here's the original patent for the truss rod. It could have said "screwing up necks since 1923"...but only if you don't understand what it does.

I remember, as a kid, Hermie, slightly slippery owner of Hermie’s Music Store in Schenectady, New York, told me NEVER to touch the truss rod on my Fender Duo Sonic. Hermie said it was factory adjusted and that it should never need readjusting and if it does, to bring it back in. That was enough for me. I never touched it. Then, when I was 17, I bought a 68 SG Standard at Manny’s in NYC and never could get the intonation right. Someone told me to adjust the truss rod. Adjust it how? Tighten it? Loosen it? I had not idea what it did and only later found out that it has very little to do with intonation and everything to do with “relief”. What a relief. It didn’t help my ill fated SG, but, years later, I eventually understood its purpose and was no longer deathly afraid of it. One of the main problems folks have when they start messing with the truss is that they have the wrong tool. Don’t try to adjust the truss rod with a pair of pliers. You’ll just bugger up the nut on a Gibson. A 5/16″ nut driver will do it if the head fits in the space allowed for it as will a socket wrench, again, if it fits in there. The best thing is a big long “T” wrench that Stew-Mac makes for the purpose. Since you’ll only be turning it a quarter turn or less at a time, the big T end is a good way to see what a quarter turn looks like. If the T goes from 12 oclock to 3 o’clock, that’s a quarter turn. If you round nut driver does a quarter turn, you better be paying attention or place a mark on the handle. Elementary stuff, right? What’s harder is figuring out just how far to turn it and in which direction. What the truss is doing is compensating for the pull of the strings which want to pull the headstock forward and cause the neck to bow slightly ( or a lot). By this I mean it will be lower in the middle than it will be at the first fret and the last fret. If it’s higher in the middle, it’s called a backbow and this usually results from a too tight truss or sometimes if the strings are left off the guitar for a very long time (like years). If the neck has a backbow, loosen the truss an eighth to a quarter turn at a time. Give the neck some time to stabilize and, if its still there, turn it another eighth turn. If you’ve loosened the truss all the way and the nut is turning freely and you still have a backbow, it’s time to get a new guitar if its a cheap one and time to see your friendly luthier if its worth saving. It’s a process that you don’t want to have to do. It sometimes requires planing the neck to level it. There are other techniques as well but that’s a different post. But let’s get back to the regular bow as its the more common issue. Few guitars are set up dead flat. Most guitars won’t play well that

You can use one of these crappy little Gibson wrenches that they give away with their high end guitars or you can use what I use.

way and will either buzz ¬†at the middle frets or fret out easily when you bend strings. This is especially true if you like your action very low. If you use your low e”E” as a straightedge, you can observe the amount of “relief” or bow the neck has. Hold the string down at the first fret and at a very high fret and see how far from the frets between those two the string sits. I’ll bet it doesn’t sit on all the frets. The less you have-the closer to flat, the more critical your setup. A bit of relief gives your strings some room to vibrate without buzzing. I like my action fairly high which would allow me to have a dead flat neck but I choose not to. I always adjust in some relief for a couple of reasons. the first is obvious-I don’t like fret buzz. The second reason is a bit more esoteric. I don’t even know if this follows any logic but it seems to work. I mentioned that the truss has very little to do with intonation and I’ve mentioned how hard it can be to intonate a 335 because you tend to run out of range on the ABR-1. Bear with me here: When you add relief, you are actually shortening the distance from the nut to the bridge by a very small increment. That changes the string length and string length is the basis for intonation. Gibsons, particularly ES-335s tend to need a pretty broad string length adjustment to intonate correctly-that is, to be in tune everywhere on the fretboard. Most of the 335’s I’ve had have the G string and/or B string saddle all the way back in the saddle. On many, I turn the saddle flat side back to get a little more length. By loosening the truss rod-adding relief, you effectively shorten the scale ever so slightly and give yourself a little more room to get the intonation spot on without running out of bridge. I don’t know how the physics works here-it seems a bit counter intuitive but it works. The larger point is when you sight down the neck of your 335 and you see a small bow, it doesn’t mean the guitar has a warped neck. It means that the truss rod needs a tweak or the guy who set it up felt that a bit of relief is just what the doctor ordered. Let me know your experiences with these kinds of adjustments. I learned setups by doing them and I’ve made my share of mistakes but the little bit of college physics I took at least helps me understand what it is I’m doing when I start adjusting things.

I use a big honkin' T wrench so I know what an eight of a turn looks like. The bigger the T, the easier it is to see how far you've turned it. Stew Mac used to sell these but I think they stopped.

2 Responses to “Fun and Games with the Dreaded Truss Rod”

  1. moxie50 says:

    I bought a cheap new bass, (Silvertone, not Sears, Samick). After doing everything I have learned to do as far a setup, I decide what the hel, might as well be a first time for the truss rod, maybe it would cure bad fret buzz. What a difference, thanksl

  2. OK Guitars says:

    Good work. No magic to it at all. And you can always put it back where it was. Just remember where you started.

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